Indicating tube system



May 31, 1949. H. G. BuslGNlEs 2,471,409

INDICATING TUBE SYSTEM Y Filed sept. 13, 1945 @'gg. l.

m comma asv/cf BVZM@ ATTORNEY Patented May 31, 1949 INDICATING TUBE SYSTEM Henri G. Busignies, Forest Hills, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application September 13, 1945, Serial No. 615,934

4 Claims.

This invention relates to cathode ray tubes which are used for indicating purposes.

In certain systems employing cathode ray oscillograph tubes, such as for example, direction finders and radar systems, the time base of the tube is rotated at a relatively low speed, such as for example, one turn per second to one turn every three or four seconds. While the direct light on the screen of the cathode ray tube as the beam strikes the screen is often observable in a fairly brightly illuminated room, the after-glow cannot beV seen except in relatively dark rooms. Because of the slow speed of rotation of the beam, visual persistence does not retain the image of the direct beam long enough to make a complete pattern of its path. These effects render such indicators unsatisfactory in yairplanes and other places where' observation is made in a fairly brightly illuminated zone.

An object of the present invention is the provision of an improved cathode ray tube for indicating purposes.

Another object of the present invention is the provision of a cathode ray tube in which the indication on the screen persists for a relatively longer time and at a relatively greater intensity, as compared with the indication of the conventional cathode ray tube heretofore employed.

Other and further objects of the present invention will become apparent and the invention will be best understood from the following description of embodiments thereof, reference being had to the accompanying drawings, in which:

Fig. 1 is a schematic side sectional View of a cathode ray tube embodying my invention:

Fig. 2 is a plan view of a magnetic eld generator used in connection with the embodiment of Fig. 1;

Fig. 3 is a partial elevational schematic View of a modified form of screen embodying my invention; and

Fig. 4 is a fragmentary, greatly enlarged, detail view of part of the screen illustrated in Fig. 3.

Referring now to the embodiment illustrated in Fig. 1, the cathode ray tube includes an envelope I having a conventional type of electron gun 2 arranged toward one end thereof and provided with any suitable deflecting means, such as deecting plates 3, for deecting the beam of electrons 4 emitted from electron gun 2. The beam 4 impinges upon a layer 5 of very ne particles of magnetic material such as, for example, a layer of iron powder, of the type for example, used in the manufacture of radio dust cores, which layer 5 is held on the inside of a preferably (Cl. Z50-164) flat portion of glass 6 forming one end of the envelope I. The layer is maintained on the glass surface 6 by any suitable means as for example, a magnetic field produced by an electromagnet magnetic eld generator l. The layer of iron dust is preferably so thick that normally no light would pass through the screen or through said layer 5. The effect of the electron beam on this layer, however, is to charge the particles thereof and cause said particles to move and be redistributed in accordance with the pattern of the beam projected on said layer. Therefore, this pattern would be formed on the dust leaving thinner and thicker areas, lines, or spots being sufficiently transparent to permit the light from a powerful source of light, such as for example, a round lamp 8 arranged on one side of the screen or layer 5, to pass through said layer and thus show the pattern suitably illuminated.

The lamp 3 may be a round lamp such as for example, of a gaseous type, arranged behind an enlarged portion 9 of the envelope I with a light screen and reflector I0 adjacent lamp 8 to direct its rays inwardly toward the iron layer 5.

The magnetic field generator may be of the type illustrated in Fig. 2 which consists of a flat spiral of wire to which electrical energy is supplied from a given source II. This may be employed to hold the layer in place and by suitably controlling the energy from control source II and thereby the resultant magnetic field, the iron powder may be redistributed after a given selected interval.

In place of the iron layer 5 and the magnetic field generator 1, a screen I2, such as illustrated in Fig. 3 and shown in greater detail in Fig. 4, may be arranged within the tube I or may form part of said tube, replacing wall 6. The screen I2 is comprised of a plurality of small metallic plates I3 overlapping each other as indicated at I4 and electrically insulated from each other as for example, by providing them with an oxide coating vor a coating of varnish at adjacent portions. The plates I3 which normally are suspended in a vertical position, are adapted to swing freely and for this purpose may be bent over, as shown at I5, a wire rod I6, a plurality of such wire rods being used for the large number of plates required. The plates are preferably very small, it being understood that the detailed showing of Fig. 4 is greatly enlarged. These plates I3 are like condenser plates and when hit by the beam 4, become charged, causing these little elements or plates to stand perpendicularly, or approximately so, to the screen and thus providing openings in the solid surface of plates normally presented. Through these openings, the light from lamp 8 passes, thus producing an illumination of the pattern traced by the beam.

The plates I3 may be suspended in front of a transparent material l1 which may be glazed and which may form one end of the envelope l of the cathode ray oscillgiaph tube. The plates may be adapted to discharge their charge by any suitable means. One way this may be accomplished is by allowing the charge to leak across the suspension rods or wires I6 to ground, or'thei suit'- able means for causing the charges to leak 01T may be employed.

While I have described the details of two embodiments of my invention, lit will be apparent that numerous changes may xbe made in these details without departing from the teach-ings of my invention. For example, While I have described the lplates I3 as being normally in closed position to present an opaque surface to the light source A8, it lWill be apparent that the plates may normally be in open position and the electron beam used to cause 'selected plates, impinged on by said beam to close, thusl producing a dark line on the bright'end Ysurface `oi the tube l. Obviously, 'other forms fof light sources than light souro'e maybe employed. Therefore While I 'have described above the principles oi my invention "in connection with specific apparatus, and particular modifications thereof, it is to be clearly'understood that this description is made onlybytva'y i'example and not as a'limit'ation -`on the scope 'o'f'iiiy invention as defined in the accomp'alnying clais.

I claiml:

l 1. A cathode ray tube comprising means producingan electron beam, beam-deecting means,

a transparent surface in the path of said beam, a layer of magnetic particles distributed on said surface normally rendering said surface opaque, and a source of light behind said surface, said particles being conditioned to move in response to the impingement of the beam upon said layer to'permit said layer to allow the transmission of iight through smeared portions for said layer.

2. A cathode ray tube according to claim 1 wherein said magnetic particles are made of iron in the form o a fine powder.

V3. cathode ray tube according to claim 1 further including means producing an electroe'ld `fo` inaintaining said particles on said surface.

A cathode ray tube comprising means produ'cing an elec'trii bea-m, beam-deflecting means, a `layer of magnetic particles arranged in the path of said beam, said layer being normally opaque, said particles being conditioned to be charged by the; irlipmgemeiit fof the beam thereqn, said particles Vmatig 'further criditicnedto move "away *from eachother 'under the leffects fof s lfih liarg'etothiln the layer at the areas which sa'i'd beam irripings.

mm1 o. BUSIGNIES.

REFERENCES errno fiile f jiiowmg rfrences are br f'reco'rd in 'the file of this patent:

uNrrn-D STATES lPivaziazu'rfs Number Name baite 2,925,143 z wrykih bec. "24, i933 1233531 'a'.wn XugJ'SO, 193s 2,175,692 rains om i'o, 'i939 2,238,137 'strung cal apr. 1'5, i911 

